Introduction
Understanding key definitions is essential for mastering Biology concepts. In Class 9 and Class 10 Biology, many exam questions are based on definitions and important terms. This page provides a collection of important Biology definitions to help students revise quickly and improve their exam performance.
These definitions cover major topics such as cells, enzymes, bioenergetics, inheritance, biotechnology, and pharmacology.
Important Definitions – Biology
1. Biology
Biology is the scientific study of living organisms and their life processes.
2. Cell
A cell is the basic structural and functional unit of life.
3. Tissue
A tissue is a group of similar cells working together to perform a specific function.
4. Organ
An organ is a structure made up of different tissues that perform a specific function.
5. Organ System
An organ system is a group of organs that work together to perform a major function.
6. Enzyme
An enzyme is a biological catalyst that speeds up chemical reactions in living organisms.
7. Metabolism
Metabolism refers to all the chemical reactions that occur within a living organism.
8. Photosynthesis
Photosynthesis is the process by which green plants make food using sunlight, carbon dioxide, and water.
9. Respiration
Respiration is the process by which cells release energy from food.
10. ATP
ATP (adenosine triphosphate) is the energy currency of the cell.
11. Nutrition
Nutrition is the process of obtaining and using food for growth and energy.
12. Autotroph
An autotroph is an organism that makes its own food, usually by photosynthesis.
13. Heterotroph
A heterotroph is an organism that depends on other organisms for food.
14. Digestion
Digestion is the breakdown of complex food into simpler substances.
15. Transport (in plants)
Transport in plants is the movement of water, minerals, and food within the plant.
16. Transpiration
Transpiration is the loss of water vapor from plant leaves through stomata.
17. Xylem
Xylem is a tissue that transports water and minerals from roots to other parts of the plant.
18. Phloem
Phloem is a tissue that transports food from leaves to other parts of the plant.
19. Gene
A gene is a unit of heredity made of DNA that controls a specific trait.
20. Chromosome
A chromosome is a thread-like structure made of DNA that carries genetic information.
21. Inheritance
Inheritance is the transmission of traits from parents to offspring.
22. Variation
Variation refers to differences in characteristics among individuals of the same species.
23. Biotechnology
Biotechnology is the use of living organisms or their products to produce useful substances.
24. Genetic Engineering
Genetic engineering is the process of modifying an organism’s genetic material.
25. Plasmid
A plasmid is a small circular DNA molecule found in bacteria.
26. Recombinant DNA
Recombinant DNA is DNA formed by combining genetic material from different sources.
27. Fermentation
Fermentation is a process in which microorganisms produce useful substances like alcohol or antibiotics.
28. Pharmacology
Pharmacology is the study of drugs and their effects on the human body.
29. Antibiotics
Antibiotics are drugs used to treat bacterial infections.
30. Vaccine
A vaccine is a substance that helps the body develop immunity against diseases.
31. Immunity
Immunity is the body’s ability to resist infections and diseases.
32. Addiction
Addiction is a condition in which a person becomes dependent on drugs.
33. Ecosystem
An ecosystem is a system where living organisms interact with their environment.
34. Food Chain
A food chain is a sequence showing how energy flows from one organism to another.
35. Food Web
A food web is a network of interconnected food chains.
36. Pollution
Pollution is the contamination of the environment by harmful substances.
37. Conservation
Conservation is the protection and proper use of natural resources.
38. Homeostasis
Homeostasis is the process by which organisms maintain a stable internal environment.
39. Osmosis
Osmosis is the movement of water across a semi-permeable membrane from low solute concentration to high solute concentration.
40. Diffusion
Diffusion is the movement of particles from an area of higher concentration to lower concentration.
41. Active Transport
Active transport is the movement of substances across a membrane using energy.
42. Chlorophyll
Chlorophyll is a green pigment that absorbs light energy for photosynthesis.
43. Mitochondria
Mitochondria are cell organelles that produce energy in the form of ATP.
44. Ribosome
Ribosomes are structures in cells where proteins are synthesized.
45. Nucleus
The nucleus is the control center of the cell containing genetic material.
46. DNA
DNA is a molecule that carries genetic information in living organisms.
47. RNA
RNA is a molecule involved in protein synthesis and gene expression.
48. Mutation
A mutation is a sudden change in the genetic material of an organism.
49. Cloning
Cloning is the process of producing identical copies of an organism or cell.
50. Gene Therapy
Gene therapy is a method used to treat genetic disorders by replacing defective genes.
Conclusion
Learning and revising important definitions helps students build a strong foundation in Biology. These definitions are useful for quick revision and are commonly asked in exams.
Students should regularly review these terms along with MCQs and written questions for better understanding and performance.